Tri-joint implant

ABSTRACT

Methods and devices are provided for replacing damaged, injured, diseased, or otherwise unhealthy elements of the spinal three-joint complex, such as the facet joints and discs. In one exemplary embodiment, a joint replacement system includes a facet replacement component that is adapted to replace and/or augment the facet joints, and a disc replacement component that is adapted to replace a spinal disc. The facet replacement component and the disc replacement component can couple to one another to allow and/or control flexion, extension, and/or lateral bending of the spine, preferably while substantially restricting posterior-anterior shear and axial rotation of the spine.

CROSS REFERENCE TO RELATED APPLICATIONS

The application claims priority to U.S. Provisional Application Ser. No. 60/575,017, filed May 27, 2004, and entitled “Tri-Joint (Disc and Facet) Implant,” which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

The vertebrae in a patient's spinal column are linked to one another by the disc and the facet joints, which control movement of the vertebrae. Each vertebra has a pair of articulating surfaces located on the left side, and a pair of articulating surfaces located on the right side, and each pair includes a superior articular surface, which faces upward, and an inferior articular surface, which faces downward. Together the superior and inferior articular surfaces of adjacent vertebra form a facet joint. Facet joints are synovial joints, which means that each joint is surrounded by a capsule of connective tissue and produces a fluid to nourish and lubricate the joint. The joint surfaces are coated with cartilage allowing the joints to move or articulate relative to one another. In combination with the intervertebral disc, the two facet joints form the spinal three-joint complex.

Diseased, degenerated, impaired, or otherwise painful facet joints and/or discs can require surgery to relieve pain or restore function to the three-joint complex. Subsequent surgery may also be required after a laminectomy, as a laminectomy predisposes the patient to instability and may lead to post-laminectomy kyphosis (abnormal forward curvature of the spine), pain, and neurological dysfunction. Current clinical data have suggested that degeneration of one member of the three joint complex, that is either the discs or the facet joints, contributes to the degeneration of the other. While implants are available for replacing either a diseased disc or the facet joints, there are no implants that can be used to replace the entire spinal three-joint complex.

Accordingly, there remains a need for improved systems and methods for repairing and/or replacing the spinal three-joint complex.

BRIEF SUMMARY OF THE INVENTION

Disclosed herein are various methods and devices for repairing and/or replacing a damaged facet joint, and optionally other elements of a patient's spine, such as the disc. In one exemplary embodiment, a facet replacement device for dynamically stabilizing the spine is provided having a first member that is adapted to couple to a first vertebra and a second member that is adapted to couple to a second vertebra adjacent to the first vertebra. The second member can be in communication with the first member to control movement of the first and second vertebrae relative to one another. The facet replacement device can also include a connector that is adapted to couple the first and/or second member to a disc replacement device that is disposed between the first and second vertebrae.

The first and second members can have a variety of configurations, but in one exemplary embodiment the first and second members are in the form of plates that are adapted to attach to a posterior surface of a vertebra. One or more thru-bores can be formed therein for receiving a fastening element, such as a bone screw, for mating the members to a vertebra. Each plate can have a variety of shapes and sizes, but in one exemplary embodiment the plates are curved to match a contour of a posterior surface of a vertebra. The plates can also have a shape that avoids contact with the spinous process. Furthermore, the plates can be plastically deformed in situ, such that the curvature of the plates can be manipulated by the surgeon during the surgery to fit the specific anatomy of each patient, in the same manner that cervical plates and lumbar rods are bent to match patient anatomy during a fusion procedure.

The first and second members can also be adapted to control movement of the adjacent vertebrae relative to one another. In one embodiment, the first and second members can be integrally formed with one another or mated to one another to either prevent or limit movement of the adjacent vertebrae relative to one another. For example, the first and second members can include a flexible connection formed there between, or at least a portion of the first and second members can be formed from a flexible material to allow limited movement of the vertebrae. In another embodiment, the first and second members can be formed from separate pieces that are adapted to move relative to one another. In one exemplary embodiment, the first and second members can include one or more bearing surfaces formed thereon and adapted to move against one another to allow the first and second members to articulate relative to each other. While the bearing surfaces can have a variety of configurations, in one exemplary embodiment the bearing surfaces can be in the form of fins that are configured to slide against one another. In certain exemplary embodiments, the fins can be configured to allow flexion while limiting or preventing extension, axial rotation, and/or lateral bending of the adjacent vertebrae. For example, the first member can have one or more longitudinally extending fins with an outwardly facing bearing surface formed thereon, and the second member can have one or more angled fins with an inwardly facing bearing surface formed thereon. The fins can be positioned such that the outwardly facing bearing surface(s) of the first member slides against the inwardly facing bearing surface(s) of the second member to allow flexion while limiting or preventing extension, axial rotation, and/or lateral bending of the adjacent vertebrae.

In another exemplary embodiment, as noted above, the first and second members can include connectors for mating to a disc replacement device disposed between the adjacent vertebrae. While the connectors can have a variety of configurations, in one exemplary embodiment the connectors can be in the form of elongate members that include a mating feature, such as threads, formed on a portion thereof for mating with a corresponding mating feature formed on or in the disc replacement member. The first and second members can include thru-bores formed therein for receiving connectors.

In another aspect, a joint replacement system is provided that includes a disc replacement member that is adapted to be disposed between a superior vertebra and an adjacent inferior vertebra, and superior and inferior facet replacement components that are adapted to couple to the superior and inferior vertebra. The disc replacement member can consist of one or more components. At least one of the superior and inferior facet replacement components can be adapted to couple to the disc replacement member. In one exemplary embodiment, the superior facet replacement component includes at least one connector that is adapted to mate to a superior portion of the disc replacement component, and the inferior facet replacement component includes at least one connector that is adapted to mate to an inferior portion of the disc replacement component.

Exemplary methods for dynamically stabilizing the posterior elements of adjacent vertebrae are also disclosed. In one embodiment, the method can include coupling superior and inferior facet replacement members to adjacent superior and inferior vertebrae. In an exemplary embodiment, the superior and inferior replacement members are positioned on a posterior surface of the superior and inferior vertebrae. A fastening element can be inserted through one or more thru-bores formed in each member to attach the facet replacement members to the vertebrae. The method can also include coupling at least one of the superior and inferior facet replacement members to a disc replacement member that is disposed between the adjacent superior and inferior vertebrae.

In other aspects, the method can include adjusting a position of the disc replacement member between the adjacent vertebrae using one or more connectors that couple the superior and/or inferior facet replacement member to the disc replacement member. In one exemplary embodiment, the connector(s) can be in the form of an elongate member having threads formed thereon for engaging corresponding threads formed on or in the disc replacement member, and the connector(s) can be rotated to move the disc replacement device closer to or farther away from the facet replacement members.

In another exemplary embodiment, a method for replacing the spinal three-joint complex is provided and includes replacing a disc disposed between superior and inferior vertebrae with a disc replacement member, attaching opposed lateral portions of a superior facet replacement member to opposed pedicles on the superior vertebra, attaching opposed lateral portions of an inferior facet replacement member to opposed pedicles on the inferior vertebra, and coupling at least one of the superior and inferior facet replacement members to the disc replacement member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an anterior perspective view of one exemplary embodiment of a joint replacement system having a facet replacement component and a disc replacement component;

FIG. 2 is a posterior perspective view of a first member of the facet replacement component of the joint replacement system shown in FIG. 1;

FIG. 3 is a posterior perspective view of a second member of the facet replacement component of the joint replacement system shown in FIG. 1;

FIG. 4 is a posterior view of the joint replacement system shown in FIG. 1;

FIG. 5 is a posterior view of another embodiment of a joint replacement system;

FIG. 6A is a posterior perspective view of the disc replacement component of the joint replacement system shown in FIG. 1;

FIG. 6B is a posterior view of the disc replacement component shown in FIG. 6A;

FIG. 7 is an anterior perspective view of the disc replacement component shown in FIGS. 6A and 6B being mated to the first and second facet replacement members shown in FIGS. 2-4;

FIG. 8 is a side view of the joint replacement system shown in FIG. 1;

FIG. 9A is a posterior view of the device shown in FIG. 1 coupled to adjacent vertebrae; and

FIG. 9B is a side view of the device shown in FIG. 1 coupled to adjacent vertebrae.

DETAILED DESCRIPTION OF THE INVENTION

Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the devices and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those of ordinary skill in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the present invention is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present invention.

Disclosed herein are various methods and devices for replacing damaged, injured, diseased, or otherwise unhealthy elements of the spinal three-joint complex, such as the facet joints and discs. FIG. 1 illustrates one exemplary embodiment of a joint replacement system 10 that includes a facet replacement component 10 a that is adapted to replace and/or augment the facet joints, and a disc replacement component 10 b that is adapted to replace a spinal disc. The facet replacement component 10 a and the disc replacement component 10 b can couple to one another to allow and/or control flexion, extension, and/or lateral bending of the spine, preferably while substantially restricting posterior-anterior shear and rotation of the spine. A person skilled in the art will appreciate that, while the methods and devices are especially configured for use in restoring and/or replacing the facet joints and disc of a patient's spine by a posterior surgical approach, the methods and devices can be adapted for use in an anterior approach, or they can be used for a variety of other purposes in a variety of other surgical procedures. Moreover, while the methods and devices are described in conjunction with a disc replacement component 10 b having a particular configuration, a person skilled in the art will appreciate that the methods and devices can be adapted for use with a variety of spinal prostheses having a variety of other configurations, or it can be adapted for use alone with the natural disc.

FIGS. 2-4 illustrate the facet replacement component 10 a in more detail, and as shown, the facet replacement component 10 a can include a first or superior member 12 that is adapted to couple to a superior vertebra, and a second or inferior member 18 that is adapted to couple to an inferior vertebra. In use, the first and second members 12, 18 can communicate with one another to control movement of the superior and inferior vertebrae relative to one another. The first and/or second members 12, 18 can also be adapted to couple to a disc replacement component 10 b, as will be discussed in more detail below.

The first member 12, shown in more detail in FIG. 2, can have a variety of shapes and sizes, but in one exemplary embodiment the first member 12 can have a shape that complements a shape of the posterior surface of a vertebra. For example, the first member 12 can be in the form of a plate having a curved configuration. The first member 12 can also have a shape that is adapted to avoid contact with the spinous process. In the illustrated exemplary embodiment, the first member 12 has a central elongate portion 17 with a wing-shaped portion 13, 15 formed on each end of the central elongate portion 17. The wing-shaped portions 13, 15 are shown extending in a superior direction from the elongate central portion 17. Such a configuration allows the central elongate portion 17 to be positioned just inferior to the spinous process on a superior vertebra, while allowing the wing-shaped portions 13, 15 to extend in a superior direction around opposed sides of the spinous process. The also facilitates mating of the first member 12 to the vertebra, as the wing-shaped portions 13, 15 can be positioned adjacent to the pedicles of the vertebra for receiving one or more fastening elements adapted to mate the first member 12 to the vertebra, as will be discussed in more detail below.

The second member 18, shown in more detail in FIG. 3, can also have a variety of shapes and sizes, but in an exemplary embodiment it has a shape that is similar to the shape of the first member 12. That is, the second member 18 can also be in the form of a curved plate having a central elongate portion 25 with wing-shaped portions 21, 23 formed on each end of the central elongate portion 25. The wing-shaped portions 21, 23 of the second member 18 can extend in a superior direction to allow the second member 18 to mate to a disc replacement device, as will be described in more detail below. However, such a configuration is not necessary to avoid contact with the spinous process of an inferior vertebra, as the central elongate portion 25 can be positioned superior to the spinous process of the inferior vertebra to allow the wing-shaped portions 21, 23 to mate to the pedicles of the inferior vertebra.

As noted above, the first and second members 12, 18 are adapted to be coupled to the superior and inferior vertebrae. Accordingly, a variety of techniques can be used to attach the first and second members 12, 18 to the vertebrae. In one exemplary embodiment, the first and second members 12, 18 can each include one or more thru-bores formed therein for receiving one or more fastening elements, such as bone screws. As shown in FIGS. 2-3, each wing-shaped portion 13, 15, 21, 23 has a thru-bore 14 a, 14 b, 20 a, 20 b formed therein for receiving a fastening element therethrough. The thru-bores 14 a, 14 b in the first member 12 are formed in a superior region 13 a, 15 a of the wing-shaped portions 13, 15 to allow the wing-shaped portions 13, 15 to be attached to the pedicles of a superior vertebra. The thru-bores 20 a, 20 b in the second member 18 are formed in an inferior portion 21 a, 23 a of the wing-shaped portions 21, 23 to allow the wing-shaped portions 21, 23 to be attached to the pedicles of an inferior vertebra. One skilled in the art will appreciate that the thru-bores 14 a, 14 b, 20 a, 20 b can have any configuration that allows them to receive a fastening element, and the configuration can vary depending on the type of fastening element used. In the illustrated embodiment, the thru-bores 14 a, 14 b, 20 a, 20 b are substantially circular for receiving a bone screw therethrough. In one exemplary embodiment, these thru-bores 14 a, 14 b, 20 a, 20 b can incorporate a polyaxial mechanism of the type commonly used in pedicle screw systems that allows for intra-operative adjustment of bone screw angulation. Other fastening elements include, by way of non-limiting example, rivets, hooks, wires, etc.

As previously indicated, the first and second members 12, 18 can also be adapted to communicate with one another to control movement of the adjacent vertebrae relative to one another. The exemplary embodiment can employ protrusions, or fins, that are positioned and geometrically configured to mimics the natural facet joints. In one exemplary embodiment, as shown in FIGS. 1-4, the first and second members 12, 18 can articulate with one another. While a variety of techniques can be used to allow articulation, in one embodiment each member 12, 18 has two fins 16 a, 16 b, 22 a, 22 b formed on and protruding from a posterior surface 12 p, 18 p thereof for allowing the members 12, 18 to articulate relative to one another. The fins 16 a, 16 b, 22 a, 22 b can be positioned at a variety of locations on the first and second members 12, 18, however in the illustrated exemplary embodiment the fins 16 a, 16 b, 22 a, 22 b are positioned on the wing-shaped portions 13, 15, 21, 23 just outward of the central portion 17, 25. The fins 16 a, 16 b, 22 a, 22 b can also be formed inward of thru-bores 14 a, 14 b, 20 a, 20 b formed in the wing-shaped portions 13, 15, 21, 23. The shape of the fins 16 a, 16 b, 22 a, 22 b can also vary, but in one exemplary embodiment the fins 16 a, 16 b on the first member 12 have an elongate shape with proximal portions 16 p ₁, 16 p ₂ that converge in an inferior direction, and distal portions 16 d ₁, 16 d ₂ that are substantially parallel to one another, and the fins 22 a, 22 b on the second member 18 have a substantially rectangular cross-sectional shape. The fins 16 a, 16 b on the first member 12 can also extend in an inferior direction beyond an inferior edge 12 i of the first member 12. This allows the fins 16 a, 16 b on the first member 12 to extend toward and bear against the fins 22 a, 22 b on the second member 18.

Each fin 16 a, 16 b, 22 a, 22 b can also include a bearing surface 16 x, 16 y, 22 x, 22 y formed thereon for slidably bearing against one another. In the illustrated exemplary embodiment, bearing surfaces 16 x, 16 y are formed on an outwardly-facing surface of the distal portions 16 d ₁, 16 d ₂ of the first member 12, and bearing surfaces 22 x, 22 y are formed on an inwardly-facing surface of the fins 22 a, 22 b of the second member 18. Each bearing surface 16 x, 16 y, 22 x, 22 y can also vary in shape and size, but in one exemplary embodiment the bearing surfaces 16 x, 16 y, 22 x, 22 y have complementary shapes. For example, the bearing surfaces 16 x, 16 y on the first member 12 can have a convex shape and the bearing surfaces 22 x, 22 y on the second member 18 can have a concave shape for slidably seating the convex bearing surfaces 16 x, 16 y of the first member 12. This exemplary embodiment can mimic the bearing surface orientation of the lumbar facets.

In use, the configuration of the bearing surfaces 16 x, 16 y, 22 x, 22 y can be effective to control flexion, extension, axial rotation, and/or lateral bending of the adjacent vertebrae. For example, the angle of the fins 16 a, 16 b, 22 a, 22 b and/or the bearing surfaces 16 x, 16 y, 22 x, 22 y on the first and/or second members 12, 18 can be adapted to limit extension and/or lateral bending of the adjacent vertebrae relative to one another. As shown in FIG. 4, the fins 22 a, 22 b on the second member 18 converge in an inferior direction, and the bearing surfaces 16 x, 16 y on the first member 12 converge in an inferior direction. As a result, when the fins 16 a, 16 b on the first member 12 are slid in an inferior direction relative to the fins 22 a, 22 b on the second member 18, the angle of the fins 22 a, 22 b on the second member 18 will eventually engage the fins 16 a, 16 b on the first member 12 to prevent further inferior movement of the first member 12 relative to the second member 18, in turn limiting extension of the adjacent vertebrae relative to one another. The angle of the fins 22 a, 22 b on the second member 18 can also limit or prevent lateral bending and/or axial rotation, as the fins 22 a, 22 b will also engage the fins 16 a, 16 b on the first member 12 to limit or prevent relative lateral movement thereof. The fins 16 a, 16 b, 22 a, 22 b on the first and second members 12, 18 are also particularly advantageous in that they can prevent antero-posterior translation and shearing of the vertebrae relative to one another.

A person skilled in the art will appreciate that a variety of other techniques can be used to control movement of two adjacent vertebrae relative to one another. For example, the fins 22 a, 22 b on the second member 18 can have one or more grooves formed therein for slidably receiving the fins 16 a, 16 b on the first member 12. The fins 22 a, 22 b on the second member 18 can, in other embodiments, include a stop formed thereon to limit movement of the first member 12 relative thereto. The stop, or all or some of the fins 16 a, 16 b, 22 a, 22 b themselves, could be formed from a flexible material to provide some shock absorption between the two members 12, 18. In other aspects, the fins 16 a, 16 b, 22 a, 22 b can be fixedly mated or integrally formed with one another. For example, a mating element, such as a pin, could be inserted through a portion of each fin 16 a, 16 b, 22 a, 22 b to mate the fins 16 a, 16 b on the first member 12 to the fins 22 a, 22 b on the second member 18, thereby preventing movement of the first and second members 12, 18 relative to one another. Alternatively, as shown in FIG. 5, the first and second members 12′, 18′ can be connected by a flexible member 100′ that allows some movement between the first and second members 12′, 18′. In other embodiments, the fins 16 a, 16 b, 22 a, 22 b can be rigid or flexible (or elastic) depending upon the needs of the surgeon, the later being particularly advantageous if the fins 16, 22 are mated together.

A person skilled in the art will also appreciate that the materials used to form the fins 16 a, 16 b, 22 a, 22 b can vary depending on the configuration of the fins 16 a, 16 b, 22 a, 22 b, and that a variety of materials can be used. Suitable exemplary materials for forming the fins 16 a, 16 b, 22 a, 22 b include, by way of non-limiting example, titanium, stainless steel, cobalt chrome, plastics such as polyethylene, polyurethane, PEEK, silicone, and polyurethane polycarbonate, and various ceramics, or composite combinations thereof. In other embodiments, the bearing surfaces 16 x, 16 y, 22×, 22 y on the fins 16 a, 16 b, 22 a, 22 b can be coated with a material that is adapted to reduce friction and wear on the bearing surfaces 16 x, 16 y, 22×, 22 y. Suitable exemplary coatings include, by way of non-limiting example, titanium nitride (TiN), titanium carbide, chromium carbide, pyrolytic carbon, diamond-like carbon, and other similar materials.

In another exemplary embodiment, as previously noted, the first and/or second members 12, 18 of the facet replacement device 10 a can be adapted to mate with a disc replacement device 10 b disposed between adjacent vertebrae. A variety of techniques can be used to mate the facet replacement device 10 a to the disc replacement device 10 b, but in one exemplary embodiment the first and second members 12, 18 can each include one or more openings formed therein for receiving a connector. As shown in FIGS. 2-4, each wing-shaped portion 13, 15 on the first member 12 has an opening 19 a, 19 b formed in an inferior region 13 b, 15 b (which can also be considered to be a terminal end of the elongate central portion 17) for receiving a connector. As is further shown, each wing-shaped portion 21, 23 on the second member 18 has an opening 27 a, 27 b formed in a superior region 21 b, 23 b thereof for receiving a connector. The shape and size of each opening 19 a, 19 b, 27 a, 27 b can vary depending on the shape and size of the connectors, however in the illustrated exemplary embodiment each opening 19 a, 19 b, 27 a, 27 b is substantially circular and polyaxial, to allow the angle of the connector to vary depending on patient anatomy.

The connectors used to mate the first and second members 12, 18 to adjacent vertebrae can have any configuration that allows the facet replacement device 10 a to mate with a disc replacement device 10 b. In an exemplary embodiment, as shown in FIGS. 1 and 7, each connector 36 a, 36 b, 36 c, 36 d is in the form of an elongate member having a head (36 h is shown in FIGS. 7 and 8) formed on one end thereof for seating within one of the openings 19 a, 19 b, 27 a, 27 b formed in the first and second members 12, 18, and having an elongate shaft with threads formed on a portion thereof for mating with corresponding threads formed on the disc replacement device 10 b, discussed in more detail below. While the connector heads can have a variety of configurations, in one embodiment the heads can be polyaxial to allow the connectors 36 a, 36 b, 36 c, 36 d to pivotally move with respect to the first and second members 12, 18.

A person skilled in the art will appreciate that the connectors 36 a, 36 b, 36 c, 36 d can have a variety of other configurations. For example, in one embodiment the connectors can be flexible to provide an elastically deformable connection between the facet replacement device 10 a and the disc replacement device 10 b. Suitable flexible and/or elastic materials include, by way of non-limiting example, polyetheretherketone (PEEK), nylon, polyethylene, titanium, Nitinol, polypropylene, polyurethane, silicone, and stainless steel. In other embodiments, the connectors can be integrally formed with the first and second members 12, 18 or they can be fixedly but rotatably mated to the first and second members 12, 18. The connectors could also be in the form of springs or other flexible members that could allow relative motion between the first and second members 12, 18. Moreover, a variety of other mating techniques can be used to attach one or both of the first and second members 12, 18 to a disc replacement device 10 b including, by way of non-limiting example, a snap-fit, an interference fit, a magnetic engagement, etc.

FIGS. 6A-6B show one exemplary embodiment of a disc replacement device 10 b that can be used with the facet replacement device 10 a. As shown, the disc replacement device 10 b has superior and inferior endplate members 26, 30 with a core 34 disposed therebetween. While the endplate members 26, 30 can have a variety of configurations, in the exemplary embodiment the superior endplate member 26 is adapted to be positioned adjacent to an endplate of the superior vertebra, and the inferior endplate member 30 is adapted to be positioned adjacent to an endplate of the inferior vertebra. Both the inner and the outer surfaces of the endplate members 26, 30 can be configured to complement the shape of the vertebral endplates and the core 34, respectively. For example, the outer surfaces of the endplate members 26, 30 can be curved to complement the curve of the vertebral endplates, and the inner surfaces of the endplate members 26, 30 can be concave to complement the convex shape of the core 34. The core 34 can also have any configuration, but in one exemplary embodiment it is substantially disc-shaped with substantially convex superior and inferior surfaces that are adapted to be received within the corresponding substantially concave inner surfaces of the endplate members 26, 30. As a result, the core 34 can pivot relative to the endplate members 26, 30 to allow movement of the adjacent vertebrae relative to one another. One exemplary disc replacement device is the Charité™ Artificial Disc available from DePuy Spine, Inc. The exemplary embodiment shown in FIGS. 1 and 6A-8 differs from the Charite Artificial Disc in that it is smaller, thereby allowing posterior insertion; furthermore, this smaller disc replacement member has mating features for attachment to the facet replacement member(s), as described below. Alternate embodiments of the disc replacement member include, by way of non-limiting example, configurations of one or more components.

As previously indicated, the first and second members 12, 18 of the facet replacement device 10 a can be adapted to mate to the disc replacement device 10 b. Accordingly, the disc replacement device 10 b can include one or more mating features formed thereon to facilitate mating thereof to the first and second members 12, 18. While the mating feature(s) will vary depending upon the configuration of the connector element used to mate the facet replacement device 10 a to the disc replacement device 10 b, in the illustrated exemplary embodiment, each endplate member 26, 30 includes opposed bores 28 a, 28 b, 32 a, 32 b formed thereon for receiving a connector 36 a, 36 b, 36 c, 36 d. In the exemplary embodiment, the bores 28 a, 28 b, 32 a, 32 b are formed between the inner and outer surfaces of each endplate member 26, 30. Where the endplate member 26, 30 has a width that is less than a width of the connector 36 a, 36 b, 36 c, 36 d being used, the region of the endplate member 26, 30 surrounding the bores 28 a, 28 b, 32 a, 32 b can protrude above the inner and/or outer surfaces of the endplate members 26, 30. Each bore 28 a, 28 b, 32 a, 32 b can also include threads formed therein for mating with corresponding threads formed on the connectors 36 a, 36 b, 36 c, 36 d. The bores 28 a, 28 b, 32 a, 32 b can, however, utilize a variety of other mating techniques depending on the configuration of the connector, as previously discussed.

In another exemplary embodiment, the facet replacement component 10 a and/or the disc replacement component 10 b can be provided as a kit. For example, the kit can include multiple facet replacement components 10 a that vary with respect to size and configuration. In particular, each facet replacement component 10 a can have a different bearing surface angle to allow the surgeon to select a replacement component 10 a that limits movement of the adjacent vertebrae as desired. Similarly, the kit can include multiple disc replacement components 10 b that vary with respect to size and configuration to allow the surgeon to select endplate members that match the endplates of the patient's vertebrae, and a core that has the appropriate height etc.

Exemplary methods for stabilizing the posterior elements of the spine are also provided. While facet replacement device 10 a and disc replacement device 10 b are used to describe certain exemplary methods, a person skilled in the art will appreciate that the method can vary depending on the configuration of each device and that a variety of other devices can be used. Moreover, the methods can be performed in any order.

In one exemplary embodiment, a discectomy and facetectomy is performed with a posterior surgical approach using techniques known in the art, and the disc replacement device 10 b is positioned between the adjacent vertebrae. In particular, the superior endplate member 26 is positioned adjacent to the endplate of the superior vertebra, and the inferior endplate member 30 is positioned adjacent to the endplate of the inferior vertebra. In one exemplary embodiment, the disc replacement device 10 b is sized similar to a TLIF cage so that it can be delivered using an entirely posterior surgical approach.

The facet replacement component 10 a can then be coupled to the adjacent vertebrae, as shown in FIGS. 9A-9B. In particular, and referring to FIG. 9A, the first member 12 can be positioned on the superior vertebra 65 such that the central portion 17 is positioned inferior to the spinous process 67 and the wing-shaped portions 13, 15 extend in a superior direction on opposed sides of the spinous process 67 and toward the pedicles 69, 71. A bone screw can then be inserted through the thru-bores 14 a, 14 b in the wing-shaped portions 13, 15 of the first member 12 to attach the first member 12 to the pedicles 69, 71 of the superior vertebra 65. The second member 18 can be positioned on the inferior vertebra 85 such that the central portion 25 is positioned superior to the spinous process 87 and the wing-shaped portions 21, 23 extend toward the pedicles 89, 91 of the inferior vertebra 85. A bone screw can then be inserted through the thru-bores 20 a, 20 b in the wing-shaped portions 21, 23 to attach the second member 18 to the inferior vertebra 85. While the first and second members 12, 18 can be implanted in any order, in one exemplary embodiment the second member 18 is positioned as desired and the first member 12 is then positioned as necessary based on the positioning of the second member 18.

While FIGS. 9A-9B illustrate the device implanted on adjacent superior and inferior vertebrae with the spinous process still substantially intact, one skilled in the art will appreciate that either all or a portion of the spinous process can be removed, and the device will still function in the same manner as discussed herein.

Referring back to FIG. 7, before or more preferably after the first and second members 12, 18 are attached to the superior and inferior vertebrae, the first and second members 12, 18 can be attached to the disc replacement component 10 b using at least one connector 36 a, 36 b, 36 c, 36 d. In the illustrated embodiment, two connectors 36 a, 36 b are inserted through the two openings (shown in FIG. 4 as 19 a, 19 b ) formed in the first member 12, and two connectors 36 c, 36 d are inserted through the two openings (shown in FIG. 4 as 27 a, 27 b) formed in the second member 18. The connectors 36 a, 36 b, 36 c, 36 d are inserted into corresponding bores 28 a, 28 b, 32 a, 32 b formed in the superior and inferior endplate members 26, 30 of the disc replacement component 10 b to engage the disc replacement component 10 b. Once connected, the facet replacement component 10 a in combination with the disc replacement component 10 b is effective to control movement of the adjacent vertebrae relative to one another. A person skilled in the art will appreciate that the disc replacement component 10 b can also be adapted to be implanted on an anterior side of the vertebrae.

The connectors 36 a, 36 b, 36 c, 36 d can also be used to adjust a position of the disc replacement component 10 b between the adjacent vertebrae. In particular, once the heads (only head 36 h is shown in FIG. 7) of the connectors 36 a, 36 b, 36 c, 36 d are seated within the openings 19 a, 19 b, 27 a, 27 b, additional rotation of the threaded connectors 36 a, 36 b, 36 c, 36 d will pull the endplate members 26, 30, and thus the disc replacement component 10 b, toward the facet replacement component 10 a. Alternatively, counter-rotation of the threaded connectors 36 a, 36 b, 36 c, 36 d will push the disc replacement component 10 b away from the facet replacement component 10 a. As a result, the disc replacement component 10 b can be positioned as desired, especially if the positioning adjustment is performed under fluoroscopic guidance. For posteriorly inserted embodiments of the disc replacement device 10 b, this positional control would serve two key functions: the risk of subsidence would be minimized by positioning the disc replacement device posteriorly over the strongest bone of the vertebral endplate; and the location of the center of rotation could be optimized by placing it posteriorly in the disc space. In other embodiments, the disc replacement component can be in the form of a wedge, such that movement of the disc replacement component in a posterior direction will increase the angle between the endplates of the adjacent vertebrae and increase lordosis to match the patient's anatomy.

The position of the disc replacement component 10 b can also be adjusted externally once the surgery is completed, e.g., to perform a post-surgical revision. For example, the connectors 36 a, 36 b, 36 c, 36 d can include magnetic heads formed thereon that allow the connectors 36 a, 36 b, 36 c, 36 d to be rotated using an external magnetic field. This is preferably performed using an imaging means, such as fluoroscopy, to view the disc replacement component 10 b and obtain the desired position. A person skilled in the art will also appreciate that the connectors 36 a, 36 b, 36 c, 36 d can have a configuration that allows them to be used to move the disc replacement component 10 b away from the facet replacement component 10 a. For example, the connectors 36 a, 36 b, 36 c, 36 d can be fixedly but rotatably coupled to the first and second members 12, 18 and they can have a length that is adapted to move the disc replacement component 10 b when the connectors 36 a, 36 b, 36 c, 36 d are mated thereto.

One skilled in the art will appreciate further features and advantages of the invention based on the above-described embodiments. Accordingly, the invention is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety. 

1. An implantable device for dynamically stabilizing the spine, comprising: a first facet replacement member adapted to couple to a first vertebra and having at least one protrusion formed thereon; a second facet replacement member adapted to couple to a second vertebra adjacent to the first vertebra, the second facet replacement member having at least one protrusion formed thereon that bears against the at least one protrusion on the first facet replacement member such that the first and second facet replacement members articulate with one another to control movement of the first and second vertebrae relative to one another; and at least one connector adapted to directly couple at least one of the first and second facet replacement members to a disc replacement member disposed between the first and second vertebrae; wherein the first and second facet replacement members are in the form of plates that are adapted to be positioned on a posterior surface of the first and second vertebrae.
 2. The device of claim 1, wherein the first and second facet replacement members are connected by an elastically flexible member that is adapted to provide dynamic stability between the first and second facet replacement members.
 3. The device of claim 1, wherein each plate includes a central elongate portion with a wing-shaped portion formed on opposed ends thereof, the wing-shaped portion of the first facet replacement member being adapted to extend around a spinous process on a posterior surface of the first vertebra.
 4. The device of claim 3, wherein the curvature of each plate is adapted to be modified in situ to allow the plate to more precisely conform to a patient's anatomy.
 5. The device of claim 3, wherein at least one of the wing-shaped portions on the first and second facet replacement members includes at least one thru-bore formed therein for receiving a fastening element for mating the first and second facet replacement members to the first and second vertebrae.
 6. The device of claim 5, wherein the at least one thru-bore is polyaxial.
 7. The device of claim 5, wherein the protrusions are formed on the wing-shaped portions of the first and second facet replacement members.
 8. The device of claim 1, wherein the first and second facet replacement members include at least one bearing surface formed thereon, the bearing surfaces of the first and second facet replacement members being adapted to slidably bear against one another during movement of the first and second vertebrae relative to one another.
 9. The device of claim 8, wherein the bearing surfaces are formed on the protrusions, and the protrusions protrude outward from the first and second facet replacement members.
 10. The device of claim 9, wherein the at least one protrusion on the first facet replacement member includes an outwardly facing bearing surface formed thereon, and the at least one protrusion on the second facet replacement member includes an inwardly facing bearing surface formed thereon and adapted to slidably seat the outwardly facing bearing surface on the at least one protrusion of the first facet replacement member.
 11. The device of claim 9, wherein the at least one protrusion on the first facet replacement member extends distally beyond an inferior edge of the first facet replacement member.
 12. The device of claim 1, wherein the at least one connector comprises an elongate member adapted to extend through a bore formed in at least one of the first and second facet replacement members.
 13. The device of claim 12, wherein at least a portion of the elongate member is threaded for mating with corresponding threads formed on a disc replacement member.
 14. A joint replacement system, comprising: a disc replacement member adapted to be disposed between a superior vertebra and an adjacent inferior vertebra; and superior and inferior facet replacement components adapted to couple to a posterior portion of the superior and inferior vertebrae, at least one of the superior and inferior facet replacement components being coupled to the disc replacement member, and the superior and inferior facet replacement components having bearing surfaces that slide relative to one another; wherein the superior facet replacement component comprises a superior plate adapted to mate to a posterior surface of the superior vertebra, and the inferior facet replacement component comprises an inferior plate adapted to mate to a posterior surface of the inferior vertebra.
 15. The system of claim 14, wherein the superior and inferior plates each have an elongate central portion with wing-shaped portions formed on opposed terminal ends of the elongate central portion.
 16. The system of claim 15, wherein the superior and inferior plates each include at least one thru-bore formed in at least one of the wing-shaped portions for receiving a fastening element.
 17. The system of claim 14, further comprising at least one connector adapted to mate at least one of the superior and inferior facet replacement components to the disc replacement member.
 18. The system of claim 17, wherein the at least one connector is adapted to move the disc replacement member toward and away from the superior and inferior facet replacement components.
 19. The system of claim 17, wherein the at least one connector comprises an elongate shaft having threads formed thereon for engaging corresponding threads formed on the disc replacement member.
 20. The system of claim 17, wherein the disc replacement member comprises a central core having superior and inferior endplate members coupled thereto, and wherein at least one of the superior and inferior endplate members includes at least one bore formed therein for receiving the at least one connector.
 21. The system of claim 14, wherein the superior plate includes at least one longitudinally-extending protrusion having the bearing surface formed thereon, and the inferior plate includes at least one angled protrusion having the bearing surface formed thereon and adapted to slidably seat the bearing surface of the at least one protrusion on the superior plate. 